ntinued. in addition, beta-agonists have been reported to produce electrocardiogram (ecg) changes, such as flattening of the t wave, prolongation of the qtc interval, and st segment depression. the clinical significance of these findings is unknown. therefore, terbutaline, like all sympathomimetic amines, should be used with caution in patients with cardiovascular disorders, especially coronary insufficiency, cardiac arrhythmias, and hypertension. seizures there have been rare reports of seizures in patients receiving terbutaline; seizures did not recur in these patients after the drug was discontinued.

n=61 reaction central nervous system tremor 16.3 18 nervousness 8.5 31.1 dizziness 7.8 3.3 headache 3.3 9.8 drowsiness 14.4 8.2 cardiovascular palpitations 7.8 29.5 tachycardia 2.6 0 respiratory dyspnea 2 0 chest discomfort 2.6 0 gastrointestinal nausea/vomiting 1.3 11.5 systemic weakness 2.6 1.6 flushed feeling 1.3 0 sweating 0 0 pain at injection site 2.6 1.6 note: some patients received more than one dosage strength of terbutaline and epinephrine. in addition, there were reports of anxiety, muscle cramps, and dry mouth (less than 0.5%). there have been rare reports of elevations in liver enzymes and of hypersensitivity vasculitis with terbutaline administration.

camp levels are associated with relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from cells, especially from mast cells. controlled clinical studies have shown that terbutaline relieves bronchospasm in acute and chronic obstructive pulmonary disease by significantly increasing pulmonary flow rates (e.g., an increase of 15% or more in fev1). after subcutaneous administration of 0.25 mg of terbutaline, a measurable change in expiratory flow rate usually occurs within 5 minutes, and a clinically significant increase in fev1 occurs within 15 minutes. the maximum effect usually occurs within 30 to 60 minutes, and clinically significant bronchodilator activity may continue for 1.5 to 4 hours. the duration of clinically significant improvement is comparable to that observed with equimilligram doses of epinephrine. preclinical studies in laboratory animals (minipigs, rodents, and dogs) have demonstrated the occurrence of cardiac arrhythmias and sudden death (with histological evidence of myocardial necrosis) when beta-agonists and methylxanthines are administered concurrently. the clinical significance of these findings is unknown. pharmacokinetics subcutaneous administration of 0.5 mg of terbutaline to 17 healthy, adult, male subjects resulted in mean (sd) peak plasma terbutaline concentration of 9.6 (3.6) ng/ml, which was observed at a median (range) time of 0.5 (0.08 to 1) hours after dosing. the mean (sd) auc (0 to 48) and total body clearance values were 29.4 (14.2) hr • ng/ml, and 311 (112) ml/min respectively. the terminal halflife was determined in 9 of the 17 subjects and had a mean (sd) of 5.7 (2) hours. after subcutaneous administration of 0.25 mg of terbutaline to two male subjects, peak terbutaline serum concentrations of 5.2 and 5.3 ng/ml were observed at about 20 minutes after dosing. elimination half-life of the drug in 10 of 14 patients was approximately 2.9 hours after subcutaneous administration, but longer elimination half-lives (between 6 to 14 hours) were found in the other 4 patients. about 90% of the drug was excreted in the urine at 96 hours after subcutaneous administration, with about 60% of this being unchanged drug. it appears that the sulfate conjugate is a major metabolite of terbutaline and urinary excretion is the primary route of elimination.